This invention relates to a packaging machine of the form-fill-seal type and more particularly to a vertical pillow type form-fill-seal packaging machine adapted to form an elongated bag-making material into a tubular form as articles to be packaged are dropped in and sealed in.
It has been known to use a vertical pillow-type packaging machine of this kind to package snack food such as potato chips. Such a packaging machine is provided with a former having a lapel-like guiding member and a tube, serving to form an elongated bag-making material into a tubular shape by means of the guiding member such that its side edges will overlap one on top of the other and guiding it to the tube. The tube is comprised of a conical member which has a wider open part at the top and a cylindrical member which extends downward from its top at which it connects to the bottom of the conical member. The bag-making material is transported downward by means of a pull-down belt along the outer surface of the cylindrical member while its side edges are sealed together longitudinally so as to make it into a tubular form. A transverse sealer is provided below the cylindrical member for sealing the tubularly formed bag-making material transversely to form the bottom of a bag and to cut off the portion of the bag-making material below the sealed position. After a specified quantity of articles to be packaged is dropped in through the conical member and contained inside the bag-making material, it is again sealed across its top part to produce a package having the articles sealed inside.
When relatively light but bulky articles such as potato chips are packaged, furthermore, such articles tend to get stuck especially near the junction between the aforementioned conical and cylindrical members. In view of such a problem, Japanese Patent Publication Tokkai 2001-206312, for example, disclosed a half-tube 100 as shown in FIG. 11 with a half portion of its cylindrical member 110 removed, as more clearly shown cross-sectionally in FIG. 12. As an elongated bag-making material F is introduced from above and transported downward along the outer surface of the cylindrical member 110, the material F can directly contact the articles and hence exert a downward force to prevent the clogging by the articles.
Japanese Patent Publication Tokko 3-17694 disclosed a bag-making packaging machine comprising a bar-shaped guiding member for introducing a bag-making material and a pair of perpendicularly disposed bar-shaped members that approach or cross each other on the downstream side for forming a bag by reducing the contact area size with the bag-making material.
When the bag-making material F is clamped by the transverse sealer 120 of the bag making machine as shown in FIG. 13, however, the portion of the material F on the open side becomes pulled towards the inside such that its effective cross-sectional area becomes reduced as shown in FIG. 14. Moreover, since the speed of the material F at which it is being pulled downward is much slower than the speed at which the articles are being dropped, the articles X being dropped inside the material F tend to be decelerated by the material F such that their length of spread L′ may increase as shown in FIG. 15. This may cause some of the articles to be caught by the transverse sealer 120, which begins to close before the articles X are completely dropped. In such a situation, if it is attempted to increase the production pitch, or to reduce the time intervals between successive supplying of articles X, the time length allowed for performing transverse sealing correctly is adversely affected. In other words, the production cannot be increased as desired in such a situation.
Another problem with the use of a half-tube 100 is that the articles tend to become oriented vertically when they settle inside the bag because of its narrowed cross-sectional area through which they must drop. This causes the products to be unsightly and it becomes necessary to carry out the stripping operation more intensely.
Similar problems are also encountered with a packaging machine according to aforementioned Japanese Patent Publication Tokko 3-17694.